1. Field of the Invention
The invention concerns an electrode connector, in particular a connector for electrodes for non-invasive recording of vital signs and therefore adapted to be applied to the skin of a patient, for example an electrocardiogram electrode comprising a foam material pad impregnated with a gel which is a good conductor of electricity and a peg also made from a material that is a good conductor in contact with the pad and having a connection head. The invention also concerns an electrode assembly comprising an electrode of this kind and a connector of this kind.
2. Description of the Prior Art
During non-invasive recording of vital signs continuously over a complete day of normal activity of the patient, who is therefore moving around, an electrode of this type is used which further comprises a flexible material disk able to deform locally to the shape of the body of the patient, one side of which is coated with an adhesive so that it can be stuck to the skin of the patient and which has a central hole so that it can be threaded over the electrode head and attached to the impregnated foam pad.
To record the signals, for example the signals constituting an electrocardiogram, several similar electrodes are placed at appropriate locations on the body, for example on the chest, of the patient in order to record the potential difference between two particular electrodes, taking one electrode as a reference potential.
FIG. 1 shows an electrode of this kind. The figure shows the foam pad 1 impregnated with an electrically conductive gel adapted to be applied to the skin of a patient. The side of it that is in contact with the skin of the patient is in contact with a base portion of the peg 2. The disk 3 with a central hole so that it can be threaded over the peg 1 and whose inner surface is coated with an adhesive for fixing the electrode to the skin of the patient is also made from a foam material.
At the end opposite its base portion 21 in contact with the pad 1 the peg 2 comprises an enlarged head 22 to which a connector 4 may be attached snap-fastener fashion.
The head 22 and the connector 4 are usually constructed in a similar way to a "popper" as used on garments.
To this end the connector 4 comprises an electrically conductive material contact member 41 adapted to bear against the head 22 of the electrode where it is held by a snap-fastener member 22 such as a split spring washer or a spring clip with two branches or any like device accommodated in the contact member 41. This assembly is in turn accommodated inside an electrically insulative material protective cap 43. A single-conductor electrical cable 44 connects the contact member 41 to a terminal of a recording device, in this example an electrocardiograph (not shown). The cap 43 may incorporate a metal shield connected by a ground braid integrated in the electrical cable to a ground terminal of the recording device to prevent the signal picked up by the electrode being degraded by radiated interference.
However, it is important that while the patient is wearing the electrodes the conductors connected to them are not subject to any unwanted movements which apply traction to the electrodes. Likewise it is important that the electrodes themselves are not subjected to impact or other forces such as may be caused by accidental rubbing. Experience has shown that even though precautions may be taken, it is not always possible to avoid these momentary loads on the wires and/or the electrodes themselves.
These stresses, impacts, rubbing, etc generate spurious voltages which constitute artefacts which are also recorded on the electrocardiogram and which make the latter difficult to read and interpret.
A conventional way to prevent such artefacts occurring is simply to immobilize the conductors connected to the electrodes by fixing them to the skin of the patient at some distance from the electrode using pieces of adhesive tape and forming a loop in the conductor so that there is some slack between the adhesive tape and the connector. This is uncomfortable for the patient, however, and not entirely effective as it does not avoid the problems associated with forces exerted directly on the electrode or the connector.
Known cup-shape electrode protector devices designed to fit over the electrode comprise a peripheral ring covered with an adhesive that is stuck onto the skin of the patient after immobilizing the conductor wire(s) between the adhesive side of the ring and the skin, once again forming a loop.
This method is more effective but still has drawbacks in that it requires some skill on the part of the personnel who fit the equipment to the patient, it means that fitting takes longer, it increases the overall size of the electrode and detaching it when the electrode is to be removed may cause the patient some discomfort.
An object of the invention is to remedy these drawbacks.